An aircraft engine comprises a series of compressors. In order for compression to be optimal, the air entering into said compressors has to be oriented. The parts serving to orient the air are downstream guide vanes. As represented in FIG. 1, a downstream guide vane 10 comprises an internal shroud 11, an external shroud 12 or casing shroud, as well as a plurality of blades 13. Each blade 13 comprises an external root 14 and an internal root 15. Conventionally, the external root 14 of a blade 13 is fixed by welding in the external shroud, and the internal root 15 is maintained in the internal shroud 11 by moulding of RTV silicone.
Such an assembly is not however viable at high temperatures, the RTV silicone then degrading rapidly. There are thus risks of uncoupling of the blades 13 with the internal shroud 11.
To overcome such a drawback, another attachment system of blades, represented in FIGS. 2 and 3, has been proposed. The system comprises in particular a first external half-shroud 20, a second external half-shroud, an upstream internal shroud 30, a downstream internal shroud 31, and a plurality of blades 23. Half-shroud is taken to mean a shroud having the shape of a half-ring. Each blade 23 comprises an external root 24 and an internal root 25. The first external half-shroud 20 comprises a peripheral annular groove 21 forming a guiding rail for the external roots 24 of the blades 23. The external root 24 of each blade 23 is able to be inserted into the annular groove 21 via an end 22 of the first external half-shroud 20. Each external root 24 is then positioned by displacement in the annular groove 21. Similarly, the second external half-shroud comprises a peripheral annular groove able to accept external roots of blades. The external roots of blades are inserted into the grooves at the level of the ends of the external half-shrouds.
After insertion of a certain number of blades 23 into the two external half-shrouds, the first external half-shroud 20 and the second external half-shroud are assembled by means of flanges, not represented. The blades 23 are then maintained blocked in the external half-shrouds. The upstream internal shroud 30 and the downstream internal shroud 31 are then assembled together to maintain the internal roots 25 of the blades 23 by a system of hooks and screws, known to those skilled in the art.
This attachment system does not enable the use of annular external shrouds, in other words external shrouds forming a complete closed ring, due to the system of inserting the blades 23 into the annular groove 21 that takes place at the ends of the external half-shrouds. Yet, using one annular external shroud instead of two external half-shrouds is advantageous, because the step of assembling two half-shrouds is avoided.